Prusa MK3 goodness

I recently finished building a Prusa Mk3 from kit. The experience was better than I expected. The metal parts are very solid and robust. The printed parts - and there are many - have amazing quality. There were only a very few places where I had to adapt or modify to get the assembly to work.

The build instructions are absolutely stellar! They provided very clear step-by-step procedures with pictures. Sometimes the pictures in the printed book (yes, there was a printed book!) were a little hard to interpret due to poor contrast of black-on-black, but the parallel online book cleared up all those questions.

The machine worked perfectly on the first try (it helps that I had experience with things like belt tension). You can print either from the SD card (a full size card) or via USB from your computer (the USB connector is the original, robust squarish design, not a small fragile micro-connector).

Repetier does work with it, although I found that I had to set the baud rate to 115200. Probably Cura works also. Prusa has a download package with several programs. One is a simplified wrapper for Slic3r Prusa Edition, but it looks like it is oriented to creating Gcode files for the SD card, not controlling the machine. The package also includes Pronterface - but this UI screen doesn't show you the actual X, Y, Z coordinates or the actual temperatures. They did make a change to the coding of the reported bed temperature from the printer, so Repetier doesn't display or graph the bed temperature even though it can control it.

From the 30,000 foot view, the MK3 is a more solid and well-engineered printer than the old plywood Printrbot Plus. On the other hand, it will be much more difficult to modify with homebrew changes; "it is what it is". It's faster, much quieter, and more precise.

The extruder assembly is a marvel of compactness: direct-drive gear, an extruder body fan, a print-cooling fan, a bed probe, and a filament sensor, all in an assembly smaller than the Printrbot extruder. Both fans are 3-wire with speed sensing; the bed probe is a miniature version with included temperature sensor for compensation, and the filament sensor has four wires - so the grand total wire count going from the extruder body to the Einsy board is pretty high indeed!

I'm looking forward to eventually installing the Prusa multi-material upgrade, especially so that I can do prints with dissolvable supports.

In a few days, the Prusa is going to move onto the favored position right next to my computer and the old Plus is going... where??? I have no idea yet.

The MK3's are hackable like pretty much all of the RepRap style printers. The problem with hacking it is that the components and design are at a level where there is very little need to change it. The cheap 3d printers have a lot of low-hanging upgrade fruit because they'start with piss-poor design and quality (with a few exceptions).

I'm sure your going to love the MK3! Prusa is redoing the multi-material upgrade for the MK3, so you'll end up with a second gen multi-material upgrade that should be more refined than the original.

The Prusa MK3 printer is incredibly quiet. I love the fact that you can have many Gcode files on the SD card with different names; the LCD display by default shows you the most recent file at the top of the list.But is its print quality really much better than the old plywood Plus? Well, yes, it's better but the differences are fairly subtle, as can be seen in these photos. These prints were all made with PET on each printer, and there has been no "cleanup" at all; the prints are exactly as I took them off the machine (with one exception).

In this first comparison of Benchy, the Printrbot version is on the left. Both are printed in PET. It took me seven tries with different settings on the Printrbot to get a print this good. The Prusa's print is the first try, using their default settings for PET.The biggest difference is in the bow of the boat, where the Prusa's geometry is just about perfect. Also some vertical lines on the wheelhouse are a little better on the MK3 print.

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In this second comparison of the dragon Adalinda, the MK3 exhibited much more "threading" than the Printrbot; it looks like a spider's web. But those threads are easy to clean up. The Printrbot's copy of the dragon had two broken front legs before the print progressed up beyond their attachment to the body. And the detail on Adalinda's head is much more clear on the MK3 print. One wing on the Printrbot dragon is broken off, but that was an accident that happened after the print was completed. EDIT: By the way, this print was at 40% scale - quite a challenge for any printer.

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One thing I had noticed for a long time on the Plus was a certain waviness on flat vertical surfaces, emanating from the corner where the printhead changed direction and fading out with distance from the corner. I had suspected this was due to mechanical vibration. The structure of the MK3 is MUCH more rigid, and the results validate my theory: the MK3 print doesn't have the vibration pattern.

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I'm converting my MK2S into to an MK2.9 (I coined 2.9 to indicate how close it is to the MK3). This is the mk2.5 upgrade with the 24v power supply, 24v heatbed, 24v hotend and Einsy board. The only thing I didn't change was the frame. I actually bought extra MK3 components so I can build a custom Haribo Edition MK3 with a taller z-axis once I finish the MK2.9 upgrade.

One thing that is interesting is that the current Prusa code is using 93% of the available flash space. They really have pushed the AVR platform about as far as it can possibly go. I would expect that Prusa/Ultimachine will come up with a drop in ARM replacement for the Einsy board withing 18 month to two years. Ultimachine already has an ARM based board, but it is a different form factor than the Rambo/Einsy boards.

I've been doing the Prusa MK.. upgrade over the last 4 or 5 days...I do take my time.

I did hit an unforseen hurdle though. When I had originally planned this out, I had assumed that the 24V heated bed would mount up the same as the 12V beds (the MK2.5 upgrade uses a 12V bed). It turns out they changed the way it mounts to the Y carriage frame. I'm anxious to get this back up and running, so I ordered a new MK3 frame and Y carriage frame. Thank god Prusa is carrying almost all of the unique parts for the MK3 now. I Also had to order the aluminum extrusions from Misumi. The untapped extrusions cut to proper length are cheap, but the tapped ones are like 4 times the price, so I'll get a 5mm tap set from Amazon and make up a plastic jig so I can do a proper job of tapping the holes.

Now to round up all of the screws I'll need on Amazon.

Guess I'll print up the extra MK3 parts I'll need. The extruder is the same, and the MK2.5 controller case seems to be a better design than the MK3 parts.